Cyclohexane equatorial bonds

Axial bonds to H in cyclohexane Equatorial bonds to H in cyclohexane... 

The conformational features of six membered rings are fundamental to organic chemistry so it is essential that you have a clear understanding of the directional prop erties of axial and equatorial bonds and be able to represent them accurately Figure 3 17 offers some guidance on the drawing of chair cyclohexane rings... 

Equatorial bond (Section 3 8) A bond to a carbon in the chair conformation of cyclohexane oriented approximately along the equator of the molecule... 

Figure 4.10 A procedure for drawing axial and equatorial bonds in chair cyclohexane.

Equatorial bond (Section 4.6) A bond to cyclohexane that lies along the rough equator of the ring. 

One is an optically inactive meso isomer cis or (Z)-isomer) and two are optically active tram or ( )-isomers. With cyclohexane, we can have equatorial and axial bonds. Thus, with tram structure, we obtain di-axial and di-equatorial bonds, and with cis structure we obtain axial-equatorial bonds. 

The six axial bonds are directed upward or downward from the plane of the ring, while the other six equatorial bonds are more within the plane. Conversion of one chair form into another converts all axial bonds into equatorial bonds and vice versa. In monosubstituted cyclohexanes, for electronic reasons, the more stable form is usually the one with the substituent in the equatorial position. If there is more than one substituent, the situation is more complicated since we have to consider more combinations of substituents which may interact. Often the more stable form is the one with more substituents in the equatorial positions. For example, in ct-1,2,3,4,5,6-hexachlorocyclohexane (see above) four chlorines are equatorial (aaeeee), and in the /Tisomer all substituents are equatorial. The structural arrangement of the /3-isomer also greatly inhibits degradation reactions [the steric arrangement of the chlorine atoms is unfavorable for dehydrochlorination (see Chapter 13) or reductive dechlorination see Bachmann et al. 1988]. 

From the geometrical similarity between piperidine and cyclohexane it may be assumed that the N-U vibration causing the dipole change in 94 is parallel to the major axis of rotation (largest moment of inertia /c) and accordingly the Q branch should be strong and the P and R bands, weak (parallel-type band). On the other hand the N-H equatorial bond in 93 has 28% parallel character (N-H bond 1110 to / ), and P, Q, and R bands of... 

First write a chair conformation of cyclohexane, then add two methyl groups at C-1, and draw in the axial and equatorial bonds at C-3 and C-4. Next, add methyl groups to C-3 and C-4 so that they are cis to each other. There are two different ways that this can be accomplished either the C-3 and C-4 methyl groups are both up or they are both down. 

This problem is primarily an exercise in correctly locating equatorial and axial positions in cyclohexane rings that are joined together into a steroid skeleton. Parts (a) through (e) are concerned with positions 1, 4, 7, 11, and 12 in that order. The following diagram shows the orientation of axial and equatorial bonds at each of those positions. 

Draw the chair conformation of cyclohexane and show clearly the distinction between axial and equatorial bonds. 

When ring flipping occurs from one chair to another, all the axial bonds become equatorial bonds and all the equatorial bonds become axial bonds. This does not matter for cyclohexane itself, but it becomes important when there is a substituent present in... 

Most contrastingly, the crystal structure of a solvate of pentaphenylstiborane with half a molecule of cyclohexane 1SS) revealed a nearly perfect trigonal-bipyramidal atomic arrangement156). A somewhat more distorted trigonal bipyramid was found for penta-p-tolylstiborane (see 179) with axial and equatorial bond lengths of 2.26 and 2.16 A respectively 157). 

Equatorial bond (Section 6.5) In the chair conformation of cyclohexane, a bond that projects outward from the equator of the ring. 

Each carbon atom in cyclohexane is bonded to two hydrogen atoms, one directed upward and one downward. As the carbon atoms are numbered in Figure 3-22, Cl has an axial bond upward and an equatorial bond downward. C2 has an equatorial bond upward and an axial bond downward. The pattern alternates. The odd-numbered carbon atoms have axial bonds up and equatorial bonds down, like Cl. The even-numbered carbons have equatorial bonds up and axial bonds down, like C2. This pattern of alternating axial and equatorial bonds is helpful for predicting the conformations of substituted cyclohexanes, as we see in Sections 3-13 and 3-14. 

The cyclohexane chair just drawn has the headrest to the left and the footrest to the right. Draw a cyclohexane chair with its axial and equatorial bonds, having the headrest to the right and the footrest to the left. 

If your cyclohexane rings look awkward or slanted when using the analytical approach just shown, then try the artistic approach Draw a wide M, and draw a wide W below it, displaced about half a bond length to one side or the other. Connect the second atoms and the fourth atoms to give the cyclohexane ring with four equatorial bonds. 

One of the six bonds (three down and three up) on the cyclohexane ring that are directed out toward the equator of the ring. The equatorial bonds are shown in green in the drawing at right, (p. 115)... 

---